Retired career diplomat Trevor Sofield, who served as High Commissioner to the Solomon Islands, has told a security summit he finds it "inconceivable" that its government did not trust Australia enough to consult us when they first thought about a pact with China.
"That would not have happened a few years ago," he told the Pacific Climate Security Summit on Monday.
Mr Sofield, who was manhandled away from the prime minister by his security detail in Tasmania last week, said Australia has "lost its way" in the Pacific where China has been scaling up its influence.
"We had a vision," he said.
"It was underpinned by the fact that if we could assist these governments reach economic security through trade and aid then they would certainly be able to manage their own affairs.
"But we've lost that vision and we've lost that trust that we developed over time."
Australia can't interact with the Pacific without engaging on climate change, according to Labor.
Pat Conroy, tipped to be Pacific and international aid minister if Labor wins government, told the summit in Canberra that Australia can be a "true partner" on climate change.
A new fund would be used for climate adaptation and renewable energy projects, tailored for the unique needs of each nation, Mr Conroy said.
Former Defence chief Chris Barrie, Australian chair of the Global Military Advisory Council on Climate Change, said "after two decades of denial" urgent action is needed to reduce energy demand and cut emissions.
"The election this week will be the most important in my lifetime," he told the summit.
"Being smart about energy is important for our future."
The retired admiral commended independent candidates for their climate policies and urged voters to take the call to action seriously.
"What happens in Australia on Saturday has consequences for us and it has consequences for our Pacific neighbours," he said.
Former president of Kiribati Anote Tong said he hoped the global community, not just Australia, would come to terms with the fact that the Pacific is the most vulnerable region, and is seeing the climate impact today.
"One of the greatest disappointments has been the politicisation of climate change," he said.
"Our survival is on the line.
"We will need to relocate - why is no-one talking about it?"
He said there needed to be a "genuine and sincere commitment" to cutting back on coal as well as the development of new energy sources.
Vanuatu High Commissioner to Australia Samson Vilvil Fare said "I don't think we have any security to defend in this region."
Australia signed a 2018 declaration that stated climate change is the single greatest threat to the livelihoods, security and well-being of Pacific people.
"They talk about a Pacific family but they don't treat it like a family," Mr Conroy said.